attest

(verb) provide evidence for; stand as proof of; show by one's behavior, attitude, or external attributes. Synonyms: certify, manifest, demonstrate, evidence. Examples: "His high fever attested to his illness." "The buildings in rome manifest a high level of architectural sophistication." "This decision demonstrates his sense of fairness."

(verb) authenticate, affirm to be true, genuine, or correct, as in an official capacity. Example: "I attest this signature."

(verb) give testimony in a court of law. Synonyms: testify, take the stand, bear witness.

(verb) establish or verify the usage of. Example: "This word is not attested until 1993."